Does personality play a relevant role in the placebo effect?

Subjective factors influencing placebo response have been a focus of numerous theoretical conceptualizations and empirical research. One such factor, individual's personality, has been linked to different clinical conditions, their expressions and treatment outcomes. Thus, there is little surprise many researchers have tried to identify placebo-prone personality over the years. Because of certain methodological and conceptual issues of the earlier studies, these efforts have not been very fruitful. However, recent scientific endeavours, facilitated by improved experimental designs and neuroimaging technology, have 'reignited the old fires'. It is now suggested that studies exploring the placebo-related personality traits, such as optimism/pessimism, neuroticism, and novelty seeking, need to take into account situational variables (e.g., positive or negative expectations, patient-clinician relationship) and relevant underlying neurobiological mechanisms (e.g., endogenous opioid and dopaminergic systems). Even though many questions still remain to be answered, such as the identification of different situational variables interacting with personality traits, exploration and better understanding of placebo-related personality would facilitate the use of placebo in clinical practice and improve the methodology of clinical trials.